Add typedefs for Densemaps containing SmallVectors to avoid repeating the SmallVector size when creating iterators for the DenseMap.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185682 91177308-0d34-0410-b5e6-96231b3b80d8
Use typedef for Densemap contraining SmallVector passed to a function to avoid repeating SmallVector size.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185683 91177308-0d34-0410-b5e6-96231b3b80d8